Global uncertainty associated with the analysis of PCBs and chlordanes in drinking water by headspace-SPME-GC/MS/MS

Abstract

Until recently, analytical results were normally stated as declared values, sporadically associated with strict uncertainty evaluation. Current trends in analytical chemistry require traceable data together with fully evaluated uncertainty. Polychlorinated biphenyls (PCBs) and chlordanes are considered in this paper from the standpoint of the uncertainty of their determination in drinking water. Using headspace solid-phase microextraction (HS-SPME) and GC-MS/MS, it was possible to reach low ng/L levels of quantification in drinking water for seven marker PCBs and two chlordane isomers, with a relative global uncertainty associated with the results of all contaminants ranging from 11 to 38%. Although the assessed relative uncertainties of the results can be considered acceptable and may even be further improved at higher concentration ranges, they may have considerable importance for levels close to the detection limits of the method, where they may represent more than 100% of variation for the stated result.

Keywords:

• Solid-phase microextraction
• PCBs
• Chlordane
• Water
• Global uncertainty

Acknowledgements

The authors wish to thank the Fundação para a Ciência e a Tecnologia (FCT) for the grant SFRH/BPD/7155/2001, and the Águas do Douro e Paiva for providing the water samples used in this work.